The neuroanatomy and physiology of a number of centrally acting peptides are being studied. These include ACTH, Beta-endorphin, alpha-MSH, Beta-lipotropin of the hypothalamic opiocortin system, LRF, SRIF, TRF, enkephalin, and Substance P. In addition, attempts are being made to isolate and characterize a number of unknown peptides, including a nicotine-like peptide of pituitary origin and anti-LRF and anti-TRF peptides from the pineal gland. The central peptide systems are being mapped with respect to their efferent projections and afferent connections. Experimental models are being developed to elucidate functional pathways.